#include<stdio.h>
int main()
{
	int n;
	scanf("%d",&n); 
	char a,b,c;
	a=n/(26*26)%26+'A'-1;
	b=n/26%26+'A'-1;
	c=n%26+'A'-1;
	printf("%c%c%c",a,b,c);
	return 0;
}
